Compound spiral



Nov. 3, 1 931.

c. w. KURIE, JR., ET AL 30,516

COMPOUND SPIRAL Filed Oct. 22. 1929 5 Sheets-Sheet ,1

INVENTOR. m a, M l w A TTORNEYS.

Nov. 3, 1931- -c:. w. KURIE, JR}, ET AL 1,830,516

COMPOUND SPIRAL Filed Oct. 22, 1929 3 Sheets-Sheet 2 I P W PAR/I501. /0

/.35 45 INIIl IEN'IORS 2 0 O I BY 0629M W0 O 90 ATTORNEYS.

Nov. 3, 1931. c. w. KURIE, JR., ET AL 1,830,515

' COMPOUND SPIRAL Filed 001:. 22, 1929 3 Sheets-Sheet 3 /35 PARABOLIC VEG TOR ANGLE o I PA /x5 I ca LJNENT3RE W I By m ATTORNEYS.

Patented Nov. 3, 1931 UNITED STATES FPATENTFOFDFICE CHARLES W. KURIE, JR., AND GLEMEN'I W.'ANKENY, OF COLORADO SPRINGS, COLORADO oonroonn SPIRAL Application filed October 22, 1929. 1 Serial No. 401,569.

This invention relates to apparatus of that type wherein a mass ofmater-ial'contained in a tank, or the like, of cylindrical form 1s moved towards, a. central orifice in: the floor U of such tank fordelivering therethrough, the material being of such character thatv it w1ll not, of itself, flow toward such orifice but must be pushed or scraped in that direction. Such motion is requisite incertain types of 19 thickeners, filters and clarifiers employed in the separation of solids out of liquid suspension. Very peculiar functions are essential the performance of a scraper blade used for this purpose as can be understood 1f be considered that a layer of material resting on the floor of such a tank and divided into concentric portions or zones of equal Width will contain in each zone a volume equal to 20 twR t1r7 where t-is the thickness of the layer, 7' the minor radius of the zone and the major radius of the zone. The ratio of the volumes of thezones varies as the squares of their median radii since such volumesequal r t1r(R r )2 or tqrRO where R0 is the median radius of the zone. Considering two zones adjacent each other which have radii. of l and2 respectively, there will be four times as .much material in the outer zone as in the inner zone. In the formation of a'scraper for moving such material uniformly through both zones so that the amount of material delivered from the outer zone to the inner zone exactly replaces the amount of material delivered from the inner ,zoneto the orifice, the shape of that portion of the scraperlblade travelling over the particular zone must be so proportioned that the angle of attack between of the median radius is. such/the radial component of the force exerted-by the blade on the obvious that this angle of attack must change at every point on the scraper so that the form of the scraper is a curve.

It has been found that an. appropriate '50 form of curve for this purpose, that is one angle of attack may be used with much adthat the movement inwardly of the mass to be the face of the blade and a tangent to the circle 7 infinite and of infinitesimalwidths,it will be t in which the scraping angle increases as the Curve approaches the central orifice, is a parabolic spiral. I 7' However, itis not found advisable to construct the scraper throughout with such a curve since, with adj acent zones ofconsiderable radii the differencein volume is relative- 1y slight compared to the volume to be moved and accordingly a-spiral inwhich the angle of attack is uniform may well be used or even a spiral in which the angle of attack decreases as the radius decreases may be found advisable. Even a combination of both the constant angle of attack and the decreasing c vantage.

Accordingly, the principal object of the present invention is to improve the form of scraper blades for the purposeset forth so delivered ,centrallywill be such asto ensure Ia constant fand even rate of delivery.

, With the abovev and other objects in view, as Willbe hereinafter apparent, the invention consists, in general, of certain novel details of con struction hereinafter fully described, illustrated in the accompanying vdrawings, and specifically claimed; 1

Inthe accompanying drawings, like characters of reference indicatelike parts in the several views, and':,

Figure 1 is a vertical sectional view taken diametrically through the axis of an apparatus for separating liquids from solids employing'a scraper constructed in accordance with this invention; s a 7 Figure 2 is a section on the line 22 of'Figure 1; I Figure 3 is a diagrammatic layout of the curve of one form'of the improved scraper; 9 Figure 4 is avie'w similar to Figure 3 showinga second form of curve; V i v Figure 5 is a view similar to F igure3 showing a third forni of curve; i v

Figure 6 is an analytical. diagram showmg the three'c'urves in their relation to the vector radius and vector angleas rectangular coordinates; c

The inventionis here'shown as-used in connection with the apparatus known as a Dorr m0 29 adjacent the opening in the form-of aparathickener, the same being set forth in a Patent No. 1,237,745, issued to the Dorr Company on August 21, 1917, the form here shown being that of Figure 3 of said patent.

Disregarding irrelevant details, it will be seen that the separator or thickener of the patent has a body formed by a cylindrical tank 10 wherein is connected frusto-c'onical partitions 11 in which is formed a central opening 12. Through this opening extends avertical power driven shaft l3 whereon is fixed one or more scraper blades 14. This shaft revolves in the direction of thearrowuln Figure 2 so that these blades force the material deposited on the partition inwardly-from the wall of the tank to the opening 12 so that it may drop therethrough. This scraperis of peculiar curvature and in the form shown in Figure 3 has 120 degrees of its curvature w the outer spiral is an Archimedean spiral of 120 degrees.

From a study of the diagram in Figure 6, it will be seen that the rate of change of the vector'radius increases as'it becomes shorter in the parabolic portion of each curve'so that the scraping angle increases; as the center is approached; the rate of change and scra" ing 'angle'isconstant through the Archime ean portion of the curve, and the rate o t-change of the vector angle and the scraping angle both decrease'fromtheouter tothe inner por'ti-on of the logarithmic curve." It isto benoted that this deviceis used inconn'ection; with the {separation ofsolids from liquids, the solids settling out of the liquids onto the partition, [It willbe seen that, at the outer part of theta-11 Which'is subject to most agitationbythemovement of the blade or'scraper, the form of the scraper isl l ch as to move the solids toward the center inan unaccelerated manner and, with alogarith- -mic spiral, in a deaccelerated manner. Also, near the center where the agitation 'isless and the material thicker, the solids are moved toward the center in 'anaccelerated manner. 'Thus, whichever of the improved forms of scraper blade is employed,there will be a constant delivery of material, to the opening, of uniform volumeper second." j'

The arrangement'of the curves, previously referred to and described, depends largely on the nature of the material under treatment. It is well known that the polar formulze forthese curves, in each instance, in-

the particular case.

cludes a constant. For example, the formulae for the spiral of Archimedes is X=A6/V, wherein A is a constant. This constant, it is to be noted, is to be selected with reference to the material to be handled, so that while the curves will be true spirals of the character set forth, yet they are not restricted to any particular spirals of such characters.

It istobe noted that the compound spiral herein'described is a great improvement over otherspi-rals, or. simple spirals for the same purpose, because the use of such compound spiral, lessens, to a point of elimination, congestion at the center and, at the same time,

greatly lessens theresistance to rotation, particularly at the outer portion of the scraper. It will "be notedthatlthis cannot occur with a simplespirallin which all of -the spiral is constructed lIlflCCOICliLIlCG with the same law throughout, because such simple spiral will either cause congestion at the center, or will greatlyresist rotation, especially atthe outer portion. It is further to be understood that, whilefthe spiral hasbeen shown as applied to athickener of the Dorrtype, it is not to herestricted to any particular apparatus, but is adapted to :be used in'any apparatus wherein it is desirable to move material from the periphery to the center of a'circ ularfloor.

" In F igure' 6, the: curves used are "transposed to rectangular coordinates in order to more clearly bring out the scraping angles,

the following equations being the equations of the curves:

wherein R isthe'vectorradiu s, G the vector angle, and A and n are-constants selected for This figure shows very clearly that with the paraboliczcurve the. scraping angle increases as the center is approached, the Archimedean curve ha s'a constant scraping angle; and the logarithmic curve has a scrapinganglewhich decreases as thejrajdius vector be comes shorter.

Having thus described the invention, what is claimed as new is i A'scraper character describedhaving the form of a spi'ral'wi'th the inner portion of the spiral curved:v to produce a constantly f decreasing scraping angle from the cen'ter outward, said spiral "being continued and curved to produce a constant scraping angle throughout the "length of the' continuation. r

scraperblade for apparatus of the character described having the form of 'a spiral with the inner'portion of the spiral cur'vdto produce a constantly decreasing scraping angle from the center outward, said spiral being continuedand curved to produce a constant scraping angle throughout the blade for apparatus ofi'the length of the continuation, said spiral terminating in an outer portion curved to produce a constantly increasing scraping angle from the second portion to the outer extremity of the spiral.

3. A scraper blade for apparatus of the vcharacter described having the form of a spiral wherein the inner portion has a parabolic spiral curvature.

4. A scraper blade for apparatus of the character described having the form of a spiral wherein the inner portion has a parabolic spiral curvature, said spiral having a second portion adjacent the inner portion and having an Archimedean spiral curvature.

5. A scraper blade for apparatus of the character described having the form of a spiral wherein the inner portion has a parabolic spiral curvature,said spiral having a secend portion adjacent the inner portion and having an Archimedean spiral curvature, said spiral further having an outer terminal portion of logarithmic curvature.

In testimony whereof we have afiixed our signatures. J

CHARLES W. KURIE, JR.- CLEMENT W. ANKENY. 

